This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective and public-health relevance: Ongoing research in our laboratory is devoted to developing animal models to measure the behavioral phenomenology related to substance-dependence disorders. In particular, we hope to identify the neurotransmitter pathways involved in the development of and relapse to stimulant dependence. Specific aims: The experiments proposed involve the differential-reinforcement-of-low-rate responding (DRL) schedule. The DRL schedule has been described as a model of impulsive behavior, and DRL performance is dose-dependently impaired by single doses of nicotine. Furthermore, repeated administration of nicotine results in profound perturbations on DRL-schedule behavior. This finding suggests that impulsivity is among the category of behaviors that exhibit sensitization to repeated nicotine exposure. Research design: The proposed experiments will evaluate whether sensitization of DRL-schedule performance is the result of dopaminergic or acetylcholinergic-receptor modifications. Nicotine and dl-amphetamine will be used to produce sensitization-induced impulsivity. The objective is to discover whether mecamylamine (a nicotinic-antagonist) can attenuate the effects of both stimulants, and if so, then sensitization of impulsivity may result from acetylcholine-receptor modification. Relatedness of the project: The animal behavior laboratory at Saint Michael's College is in its infancy but has already become an excellent resource for the students in psychology to engage in an active research program.